The first minute
A student has just told you something serious. What you do next decides whether the truth is preserved, contaminated, or buried. Most adults, untrained, make it worse with kindness.
The script
Listen. Do not interrupt. Do not ask leading questions. Do not promise confidentiality you cannot keep. Say, "Thank you for telling me. I believe you. I have to share this with the safeguarding lead because that is how we keep you safe." Then write down, verbatim, what was said, with the date and time.
What not to do
Do not investigate. Do not confront the named adult. Do not tell other staff in the corridor. Do not ask the student to repeat the story to anyone else. Your job is to receive and report, not to verify.